This update is for bug fixes and exploit fixes. Your save games will not be affected. However, if you have saved a game with broken multiplayer triggers (like doors missing etc). I would suggest you start from a new save after getting the update. Players could still Host using an old broken save (missing doors, items that can't be picked up). The update can't fix that unless they Host with a new save. So maybe it will take a while for all the issues to finally disappear. I hope that makes sense. It's been quite complicated :)